Stator vane locking key



Dec- 1, 1959 o. E. RIDLEY m-AL 2,915,281

STATOR VANE LOCKING KEY Filed June 5, 1957 2 Sheets-Sheet l -L` ZW 6 f45 i 1 J E 1 4Z im O f 24 2a Dec. l, 1959 o. E. RIDLEY ErAL 2,915,281

sTAToR VANE LOCKING KEY Filed June s, 1957 2 sheets-sheet 2 A rue/vir-United Safes Patent The present invention relates to a stator vaneassembly construction for use in'gascompressors or turbines the typeused in gas turbo engines.

In -U.S. application No.` 629,075 led by Robert M. Oppenheimer on Dec.l18, I1956 and assigned to the same assignee as the presentapplicationthere is described a stator vane assembly in which the stator vanes ofeach stage are carried by a statorfring made up of two halves. Thecasing is also made up of two halves and each half ofthe ring issupported in its half of the casing by meansy of cooperating ring landcasing rabbets. The splits between the halves of each stator vane ringand the casing lie substantially in the-same plane. `A number of longthin locking strips are used to lock` the half rings against rotation inthe casi-ng.

The particular stator vane assembly design described in the abovementioned application is particularly suitable for vusein very smallturbo engines of the type described in application Serial No. 548,987-led by G. W. Lawson on November`25, 1955 and assigned to the sameassignee as lthis application. It has been found, however, that-V thissmall engine design doesenot lend 2,915,281 atented Deliby l, 19,5?

rice

it requires a great deal of time therebymaking-.manufacture'andmaintenance expensive. Y f' In accordance-withthe-*present invention; a' locking mechanism for locking stator -vanerings-agains'trotation in their casing'is provided which Ye'mplo'ys'keysof1 the above mentioned type, in which eachke'y 'has an -interlockingportion movable into interlocking relationship with other interlockingpartsvof the mechanism'to'lock it in its proper position at thetimeitis-assembled-in that-position so that it cannot fall out into thecasing l duringsubsequenti assembly land disassembly of theother partsof the unit, in which thekeys-imspite` oftheir small size can beeasilyassembled in they unit without droppin-gv theminto the; casingunit,lin which-improper; assembly of the keys is.- avoided; whichsimplifies' and reduces the time required for'assembly and disassemblyof the unit and which'thereby reduces the cost' of: manufacture' andmaintenance. 'This is accomplished without additionalrseparate partssuchasvscrewsfor bolts orthe like.,4 'i.' .1. t.

Briefly stated and in accordance with #one aspectwoff the invention, the'interlocking part of the key is fmovable into and outof-interlocked.relationship with a cooperating interlocking .part of thering while such part vof the ringis removed Ifrom its casingsegment,`the key. having a portion whichcan be grasped rmly in=theiingers-to move the interlocking part thereof intofand out of suchitself to the use of the thin locking strips because with such enginesthe strips are so thin and small and fragile they are diicult to'handleiand manufacture and-are very easily assembled improperly resulting indamage to the rotor blades and possible failure of the engine.

These locking strips can be eliminated by designing the rings so thatthe edges of the halves thereof abut against each other with anindividual locking key being provided for each casing rabbet and itsassociated ring rabbet or rabbets. The key is anchored or locked betweenthe abutting edges of the halves of the casing rabbet and is located inaY recess in one of such edges. It extends between the abutting edges ofthe halves of the lring rabbet or' rabbets supported by' such casingrabbet into a recess in one of such edges 'to vthereby lock the ringhalves against rotation in the casing.Y However, the use of such keys insmall engines of the type described in the Lawson application presents aproblem because the keys are so tiny that it is difficult to assembleIthem without dropping them into the casing and theyl are very easilyassembled improperly in their recesses. After the keys have been placedin their recesses and before the other half of the casing is moved intoplace there is nothing to hold them there and they are apt to fall outinto the casing, especially when they have not been seated properly in'the rst place. lFurthermore,

the handling of the required large number of such small,

interlocked relationship. Slidingy 'movement' into as^4 sembledvpositionin its casing segment oflsuch 'part-l of the ring with the keyinterlocked therewith movesfthekey intoA itsproper locking position=withrespecteto they ring and casingnsegment: ,A 'portion-of thecasingseg--l ment overlyingtthe keyfwhen it is moved to vthis lpositionlocks the interlockingfpartsof ythe key and ringagainst moving out. of.v interlocked relationship. Movement of the interlockingI part of thering out of-its casing segment carries thefy key with it to a'positionin which the casingl segmentnoflonger locks together therinterlocking'parts and the key can be grasped byv the lingers and movedout of interlocked relationship with the ring.' 7

`Preferably'the key-.is` provided fwith `a locking=hook whichy comprisesits .interlocking parti-andthe ring seg-L ment, hasa`1.hookengagingfportion whichteorriprises` itsl interlocking part, s othat: the keyf can. be-'hookedontoV the ring segrrrenty while its :hookengaging portion isfremoved from its casing, segment.:'1hering'segmentis then slid -intozits'easingfsegmenttand `.t'hegkey'whichlisi hookedato it. is moved withpitinto .the 1properlo'cking positionwith respect to theedgesfof the ring and casing segments. A portion 'ofthecasing. segment overlying the key `when itis moved to .this positionlocks it inlitsf longer overlies it4 whereupon itr can be unhooked-fromthe'ring segment. The: above. and' 'others-advantages' lof the 'presenteinjvention will. be apparent from the` following descriptionvv v andYclaims and the accompanying drawings `all=ofv'vhilchv describe by way ofillustration only and without'lirriit'a tion'wha't now isconsidered tobe a prefe'rred'embdi-'l ment vrof the present invention." I n,

Figi 1isaviewvin'elevation and partly in section y a pa'uftloffth'-e`lower'halfjof'a compressor which lis in construe ontfotheV compressordescribed in the,abovg mentined Oppenheimer application fand which anembodiment of the locking mechanism of the,presentz invention.,`

`Fis- VA2 is la, .View in perspective similar to.V thatshowiv in Fig. 1with a lower half ring partially removed from its casing half to exposeits ,hook engaging portion and with the key associated with such halfring removed therefrom. v

Fig. 3 is a view similar to Fig. 2 showing the key hooked to the halfring but with the half `ring still partially out of its casing half.

Fig. 4 is a view taken along the line 4-4 of Figx 3.

Fig. 5 is a section taken along the line 5 5 of Fig. 1, showing the keyin its assembled position and showing in broken lines a portion of theedge of the top half of the casing and the top half ofthe ring.

Fig. 6 is a view taken along the line 6-6 of Fig. 5. ,Fig.` 7 showsanother embodiment of the locking key of; the present invention. u

Fig. 8 is a View similar to Fig. 1 but showing a smaller portion and inwhich the key of Fig. 7 is installed.

Fig.,9 is a view similar to Fig. 1 showing another Yembodiment oft'hepresent invention.

Referring to the iigures, 2 is a compressor comprising a stator vanecasing 4, having an upper half 6 and a lower half 8 joined by means offlanges 10 and bolts12 as shown in Fig. 5, and a rotor 14 comprising arotor drum 16 and rotor blades 18.

Each of the halves of the casing 4 is made up of a relatively thinsemi-cylindrical casing wall .having a plurality of spaced T-shapedrabbets 22 extending radially inwardly thereof and circumferentiallytherearound. Each T-shaped rabbet comprises a base portion 24 whichextends radially inwardly into the narrow stem 26 of the T, which inturn extends into the flange or tongue portions 30 forming the web ofthe T and extendingat right angles from the stem 26 in opposite axialdirection. Each tongue has a radially outwardly facing supportingsurface 34 and forms with the stem 26 and the shoulder 32 between 24 and26, a recess 42 so that each rabbet.

22 has a pair of recesses 42 on opposite sides thereof. j A pluralityof4 stages or rows of stator vanes 58 are mounted on a plurality oftiexible halt` rings 60 made of a thin flexible and resilient steel andthe ring halves are in turn mounted on the casing halves in spacedrelationship with casing wall 20 by means of a pair of otset,semi-annular rabbet portions 64 which are located along opposite sidesof each ring 60, each of which comprises a portion 67 extending radiallyoutwardly and a portion 68 extending in an axial direction from portion67, and which are received in oppositely facing recesses or spaces 42 ofadjacent rabbets 22, as shown, with the radially inwardly facingsurfaces 69 of the portion 68 thereof engagingand rigidly supported .bythe radially outwardly f facing surfaces 34 of the adjacent rabbets 22.The casing rabbet recesses 42 Vare radially wider than the thickness ofportion 68 (Fig. 1). Rotor blades 18 extend between adjacent rows ofvanes and a chamber 70 is defined by adjacent casing rabbets, the ringlocated between the adjacent casing rabbets and the inner surface of.shell 20 located between the adjacent casing rabbets.

All. of the above is described in detail in the above mentionedyOppenheimer application.

- In accordance with the present invention the edge 71 of eachsemi-annular T-shaped casing rabbet 22 inthe lower half of the casinghas a recess 72 extending axially thereacross, such recess having abottom surface, a radially inwardly facing wall 74 and a radiallyoutwardly facing wall 76. V'I'he corresponding edge of the axiallyextending portion 68 of each ring rabbet also has a cooperating recess78 therein, having a bottom surfacel 80 and a side wall 82. The depth ofthe ring rabbet recess 78 is the sarneas the depth of the casing rabbetrecess 72 and when the half rings are in assembled'position in thecasing half, the recess 72 in the edge of the T-shaped casing rabbet 22and the recesses 78 in the corresponding edges of the two ring rabbetsbeing supported by such casing rabbet form a single recess deiined by abottominade up of bottom surface of the casing rabbet recess and the twobottom surfaces 80 of the recesses in the two ring rabbets, a wall 74, awall 76, a wall 82 of the recess in one ring rabbet and a Wall 82 of therecess in the other ring rabbet. The non-recessed portion 84 of the edgeof the lower half 60 of each ring including the edge of portion 67 isflush with the coresponding non-recessed portion 88 of the edge of thelower casing half, the portion 88 also including the non-recessedportion of edge 71 of the casing rabbet.

One of the rabbet portions 68 of the two ring rabbets 64 supported byeach casing rabbet 22 has a notch or slot 92 therein spaced from therecess 78 as shown, the portion of 68 between the recess and notch beingdesignated as 94.

Associated with the edge 71 of each T-shaped casing rabbet is a lockingkey 96 having a locking portion 98 which is received in the recessformed by recess 72 in the edge of the casing rabbet and the tworecesses 78 in the edges of the two ring rabbets supported byy suchcasing rabbet, as shown, and which has a leg 108 extending from thelower surface thereof. The leg 100 in turn extends into a hook or foot1Q2 which is received in the notch 92 as shown in Figs. 3 to 5. Thethickness of portion 98 is the same as the depth of the recesses 72 and78 so that the top surface of 98 is ush with the non-recessed edges 84and 88 of the lower half rings and lower casing half respectively whenthe lower half rings are in assembled position in their casing half asshown in Figs. 1, 5 and 6.

When the two halves of the casing are bolted together the edges 84 ofthe lower halves of the rings and edge 88 of the lower casing half abutsnugly against the nonf recessed edges 86 of the upper halves of therings and the non-recessed edge of the upper casing half respectively(see Figs. 5 and 6). The locking portion 98' is held rmly between thebottom surface of the vrecess 72 in the edge of the'lowercasing rabbethalf and tho adjacent edge 90 of the other half of the rabbet in theupper casing half, as shown in Figs. 5 and 6. Since the bottom surfaceof the recess 78 in the edgeof the portion 68 of the lower half of eachof the two ring rabbets supported by the casing rabbet abut against thelower surface of portion 98 and the edge 86 of theportion 68 of theupper half of each of such ring rabbets in the upper casing half abutagainst the upper surface of the portion 98, the half rings are lockedagainst rotation in the casing.

When the two casing halves containing the ring halves assembled thereinare removed from each other the locking key 96 cannot fall out ofposition because of the hook 102 in the notch 92. The engagement of theedge 186 of portion 98 with the Wall 74 of recess 72 and the leg 100with the shoulder 32 o f the casing rabbet prevents the key from beingmoved radially loutwardly and consequently prevents the hook 162l frombeing removed from the notch'92 when the lower half ring'is assembled inthe lower casing half as shown.

The key can be removed simply by sliding thelower half ring containingthe recess and notch partially out of the casing half to the positionshown in Figs. 2, 3`

and 4 whereupon the key can be easily removed bymcre ly moving it in aradially outward direction.

The assembly of the unit is simple, requiring only that one end of eachhalf ring with the vanes attached thereto be inserted into one nend of aspace 70 with the rabbets 64 of the ring being inserted `into theoppositely facing recesses 42 of adjacent rabbets 22 whereafter the halfring is slid circumferentially around the recess into the positionsshown in Fig. 2. Then the key can be easily grasped by the fingers andslipped into place cn the half ring partially removed from the casingand having the notch by moving it radially inwardly thereby moving thehook 102 into the notch 92 and at the saine time the locking portion 98into the recess 78, thereby hooking the key on the ring rabbet andinterlocking them together, as shown in Figs. 3 and 4. Thereafter thehalf ring with the locking key hooked thereto is slid all the Way intoassembled position in the casing, as shown in Fig. 5, the lockingportion 98 moving into locking position in the recess 72 in the edge ofthe casing rabbet and the recess 78 in the edge of the portion 68 of theother half ring. The key associated with the other edge of the lowerhalf of the casing rabbet 22, shown in Fig. 3, and the othercorresponding edges of the lower halves of the ring rabbets supported bysuch casing rabbet is hooked in the same way to the ring rabbet of thelower half ring shown in assembled position in the casing half -in Fig.3 while it is partially removed from the other edge of the casing halfsince'the half ring shown in Fig. 3 partially removed from the casinghalf cannot be slid out of the other edge of the casing halfonce the keyis hooked thereto. Another alternate construction of these other edgesis to make them non-recessed, the recesses and notch being provided inthe edge of the upper half of the casing rabbet and the correspondingedges of the.

upper halves of the ring rabbets abutting such other edges. However,only one key is needed for each cornplete ring so that it is notessential to provide another key for these other edges. 'After all thehalf rings and keys are assembled in their casing halves, the twohalvesY ber of such tiny discs being held in place only by gravity itwill be realized that it is very easy for some of them;

to fall out of their recesses into the casing during assembly, in manycases without the assembler even knowing that it has happened. Theseloose keys which have fallen into the casing are apt to cause `damageduring operation of the compressor and furthermore the particular ringswith which they were intended to be associated are not locked againstrotation around the casing. Even Aif the assembler is aware that thekeys have fallen into the casing it is time consuming to remove them.Furthermore, it is difcult to handle such small parts since there isvery little to hold onto and consequently while they are being assembledin their recesses they are prone to slip out of the lingers into thecas-ing. They have to be dropped into the recesses and consequently theyare prone to assume improper positions. This also increases the tendencyof the small keys to fall into the casing interior.

In accordance with the present invention each key is like a clip or hookand is in effect very easily clipped or hooked on the ring segment inthe position shown in Fig. 3. It can be firmly held in the lingers whileit is being so hooked or clipped so that the danger of its slipping outof the lingers is reduced. Once -it is hooked or clipped on the ringsegment there is very little danger of it falling out during the time ittakes to move the ring segment with the key hooked thereto into place inits casing segment. It can be kept in its hooked position on the ringsegment very easily merely by the pressure of the finger while the ringsegment is being slid into place. Furthermore, the key is alwaysassembled in the proper position in its recess since once it is pushedinto the notch and recess it cannot help but be moved into properposition when the ring segment is slid into place. Although it cannot beremoved when the ring segment is assembled in its casing half because ofthe casing recess wall 74 and the shoulder 32 of the casing rabbet it iseasily removed by merely sliding par-t of the ring segment from thecasing half. It is locked in place by an interlocking of the parts ofthe key, the ring segment and the casing segment and withoutanyadditional separate part such as a screw or bolt.

As described in the above mentioned Oppenheimer application the halfrings are supported rigidly by the supporting surfaces 34 of the casingrabbets 22 but are 6 spacedfrom the shell 20 of the casing and theshoulders 32 so that they are not rigidly supported against movement ina radially outward direction, the rin-g rabbets being yieldablyheldagainst the 'radially outwardly fac-A ing supporting surfaces of thecasing rabbet rby air presi sure in chambers 70. The keys are sodesigned that the radially inwardly facing surface of the'leg 100 isVspaced a sufficient distance from therradially outwardly facing surface34 of the tongue 30 so that the key`does not interfere with thisfeature. That is, the sum of the radial thicknesses of the leg andportion 68 of thefring rabbet is less than the radial width of space 42.Further` with respect to the more, the key has some radial play casingrabbet.

The recesses and notches can be located in the top halves of the casingand rings, in which case the keys are clipped or hooked on the tophalves of the rings andl the top half of the casing holds the keys inclipped position. Furthermore, the notch can be in the lower half' ofthe ring and the cooperating ring and casing recesses inthe top halvesof the rings and casing, or the casing recess can be in the lower halflof the casing and the" ring recesses and notch in the upper half orvice versa or the casing recess can be in the top casing half, the notchin the top ring half and the ring recesses in the lower ring half.Furthermore, both the adjacent edges of the top andvbottom halves of therings and casing can be recessed so that the portion 98 is locatedpartly in the recesses in the edges of the top halves `and partly in therecesses in the edges of the bottom halves. The terms bottom and top andupper and lower are used herein only for the purpose of simplifying thedescription;y and they are not intended to limit the invention in anyway because what is Ifbottom and lower becomes top and upper and viceversa whenv the unit is turned upside down. Although a compressor hasbeen described having two halves, thepresent invention is invention inwhich the locking portion of the key has a` pair of legs 112 and 114each of which has a locking hook 116 and 118 respectively and theportion 68 of the ring rabbets of both of the ring halves associatedwith each casing rabbet have notches similar to notch 92. In such case,in clipping the key in place, both-of these ring halves must bepartially removed from the casing half to positions similar to theposition occupied by the single partially removed half ring in Fig. 3whereupon the key is slipped in place by sliding each foot into itsnotch and the locking portion `98 into the recesses 78 in the edges ofthe rabbets of both half rings whereafter both rings are pushed intoplace at the same time and occupy the positions shown in Fig. 8. Thelocking portion 98 is moved into locking position in recess 72 when thehalf rings are pushed into place. In such case the key associated withthe other adjacent edges of the half rings and casing halves mus-t beclipped to the edges of the top halves of the ring rabbets and therecesses are located in the top halves of the casing and ring rabbets.

Fig. 9 shows a ring and casing construction exactly like that shown inthe above mentioned Oppenheimer application in that each ring has twostages of vanes and has a radially outwardly extending steadying rim orrabbet "1-20 intermediate thereof between the two stages of varies. Thisrim cooperates with a steadying rim or rabbet 122 extending radiallykinwardly from the casing shell' bei tween adjacent T-shaped rabbets,all as described in the 7 above mentioned application. In theconstruction of Fig. 1 these steadying rims or rabbets are omitted.However, this does not affect the operation of the compressor or thelocking mechanism of the present invention.

We claim:

l. A stator vane assembly comprising an annular casing made up of atleast two casing segments, an annular stator vane ring mounted in saidcasing, said ring being made up of at least two ring segments, said ringhaving an annular segmented rabbet, said casing having an annularsegmented casing rabbet cooperating in circumferential engagement withthe ring rabbet to support said ring in said casing, a looking keyhaving a locking portion located between the adjacent edges of adjacentring segments and the corresponding adjacent edges of the casingsegments containing said ring segments for locking said ring segmentsagainst rotation around said casing, said locking key and one of saidring segments having a hook and the other a hook engaging portion forengaging said hook and securing said key on said one of said ringsegments and against falling out of locking position with respect to theedge of said ring segment when said ring segment is disassembled fromsaid casing segment, a portion of the casing segment in which said oneof said ring segments is located overlying said key when said ring-segment is in assembled position in said casing segment to lock saidhook against moving out of engaged relationship with said hook engagingportion.

2. An assembly according to claim 1, said one of said ring segmentshaving said hook engaging portion which comprises a notch therein spacedcircumferentially from the edge thereof and said =key having said hookwhich is receivable in said notch to hold said `key on said ring segmentwith said locking portion in looking position with respect to the edgeof said ring segment, said hook and looking portion of said key beingslidable into and out of said notch and said locking positionrespectively lto hook and unhook said key to and from said ring segmentrespectively when the portion of said ring segment having said notch isremoved from its casing segment.

3. An assembly according to claim 2 wherein each of said casing segmentstogether with its ring segment assembled therein comprises a casing andring segment assembly, said adjacent edges of said adjacent ringsegments and adjacent casing segments abutting against each other whenthe casing and ring segment assemblies are assembled, a recess in atleast one of the abutting edges of the rabbets of adjacent casingsegments, a recess in at least one of the corresponding abutting edgesof the rabbets of the adjacent ring segments contained in said adjacentcasing segments, said locking portion of said key lying in saidrecesses.

4. A stator vane assembly comprising a casing made up of at least twosegments, a stator vane ring in said casing made up of at least twocorresponding segments, said ring having an annular ring rabbet, saidcasing having an annular casing rabbet for cooperating with said ringrabbet to support said ring in said casing, each of said casing segmentstogether with its ring segment assembled therein comprising a casing andring segment assembly, the adjacent edges of adjacent ring and casingsegments abutting against each other when the casing is assembled, arecess in the edge of the casing rabbet of a casing segment and in thecorresponding edge of the ring rabbet of a ring segment mounted in saidcasing segment, a locking key having at least a portion thereofreceivable in said recess and fitting snugly between the bottom of therecess and the adjacent edges of the ring and casing rabbets of theadjacent ring and casing segments, a notch in the rabbet of the ringsegment having said recess, said notch being spaced circumferentiallyfrom said recess in said ring segment, said key having a locking hookextending into said notch to prevent said looking portion of said keyfrom accidentally falling out o'f 'said recess in said ring segmentduring assembly and disassembly and While the casing and ring segmentas# in which said recess and notch are located is moved out of itscasing segment, said locking portion of said key being movable with saidring segment while it is hooked thereto, into and out of said recess insaid casing rabbet when said portion of said ring segment is moved intoand out of said casing segment respectively, a portion of said casingsegment which contains said ring segment overlying said key and therebylocking said key against movement of said hook in a radial direction outof said notch when said ring segment is in assembled position in saidcasing segment, said movement of said locking portion of said key intoand out of said casing recess moving said lkey into and out of overlyingrelationship with said portion of said casing segment respectively.

5. A stator vane assembly comprising an annular casing made up of atleast two casing segments, an annular stator vane ring mounted in saidcasing, said ring being made up of at least two ring segments, said ringhaving an annular segmented ring rabbet, said casing having an annularsegmented casing rabbet for cooperating in circumferential engagementwith said ring rabbet to support said ring in said casing, each of saidcasing segments together with a ring segment assembled thereincomprising a casing and ring segment assembly, a locking key formed witha locking portion located in a recess in one of the abutting edges of atleast one of the casing rabbet segments and in a recess in acorresponding abutting edge of at least one of the ring rabbet segments,said locking portion cooperating with an abutting edge of an adjacentring rabbet segment and with an abutting edge of an adjacent casingrabbet segment for locking said ring segments against rotation aroundsaid casing, said locking key formed with a hook, a notch spacedcircumferentially from said abutting edge formed in one of said ringrabbet segments, such that said locking key is movable into and out ofinterlocking relationship with said one of said ring rabbet segmentswhen the ring segment associated therewith is disassembled from thecorrespondfing one of said casing segments, said one of said casingsegments securing said locking key against movement relative to said oneof said ring rabbet segments when said ring segment associated therewithis assembled with said one of said casing segments.

6. A stator vane assembly comprising an annular casing made up of atleast two casing segments, at least two annular stator vane ringsmounted in said casing, each of said rings being made up of at least tworing segments, each of said rings having an annular segmented -ringrabbet, said casing having annular segmented casing rabbets forcooperating in circumferential engagement with said ring rabbets tosupport said rings in said casing, each of said casing segments togetherwith the ring segments assembled therein comprising a casing and ringsegment assembly, a locking key formed with a locking portion located ina recess in an edge of at least one of the casing rabbet segments and ina recess in a corresponding edge of at least one of the ring rabbetsegments of each of said rings, said locking portion cooperating with anedge of an adjacent ring rabbet segment of each of said rings and withan edge of an adjacent casing rabbet segment for locking said ringsegments against rotation around said casing, said locking key formedwith at least two hooks, a notch formed in said one of said ring rabbetsegments of each of said rings and spaced circumferentially from saidedge thereof, such that said locking key is movable into and out ofinterlocking relationship with said one of said ring rabbet segments ofeach of said rings when said ring segments are disassembled from acorresponding one 'of said casing segments, 'said one of 'said casingsegments securing said locking key against movement relative to said oneof said ring segments of each of said rings when said ones of said ringand casing segments are assembled.

Cil

References Cited in the file of this patent UNITED STATES PATENTS HowardJan. 13, 1953 Wheatley et al Lune 2, 1953 10

